using npm programmatically

npmDo

function withNPMDirDo(func) {
    exec('npm bin -g', function(code, out, err) {
        var npmBinDir = String(out).trim(),
            npmlibDir = path.join(npmBinDir,  '..',  'lib',  'node_modules',  'npm');
        func(null, npmlibDir);
    });
}
 
npmDo = function npmDo(/*command, orgs..., callback*/) {
    var args = Array.prototype.slice.call(arguments),
        cmd = args.shift(),
        cb = typeof args[args.length-1] === 'function' ? args.pop() : function(err, result, current) {};
    withNPMDirDo(function(err, npmDir) {
        var npm = require(npmDir),
            npmconf = require(path.join(npmDir,  "node_modules",  "npmconf")),
            nopt = require(path.join(npmDir,  "node_modules",  "nopt")),
            configDefs = npmconf.defs,
            shorthands = configDefs.shorthands,
            types = configDefs.types,
            conf = nopt(types, shorthands);
        npm.prefix = someDir; // FIXME how to correctly set cwd for npm?
        npm.load(conf, function (er) {
            if (er) { process.stderr.write(er);  return }
            try {
                npm.commands[cmd](args, cb);
            } catch(e) {
                cb(e);
            }
        });
    });
}